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ES9038Q2M Board
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Old 9th February 2018, 10:10 AM   #171
Blackfear is offline Blackfear
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Hello
Attached how LPF Buffer looks like.
It seems, if i did not make calculation mistake or mistake by measuring, that
capacitors are only 11 a 22pf and cut off frequency then should be around 1.4Mhz which is too high, if new caps would be 100 and 220pf and rezistors remained so new freq. would be around 140khz which should be OK for 9038q2m, so i will try to remove smd caps and replace by 2.5mm pitch wima FKP, maybe i will make my own simple PCB as the replacement of current analog stage and will cut off directly onto pcb from DAC out signal before input rezistors 6.2k, also would like then to replace opamp by HDAM discrete board or discrete HDAM op amp which will be newly mounted on "new" experimental board....can anybody also check if caps are only 11 and 22pf ? so small capacitors are hard to measure onto desc...or why there is so high cut off LPF freq, can anybody explain (only if i didnt make mistake) ??
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File Type: pdf LPF DIFF BUFFER.pdf (151.7 KB, 157 views)
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Old 10th February 2018, 09:02 AM   #172
xx3stksm is online now xx3stksm  Japan
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Default capacitors value

I measured the registers and capacitors of my board (Ver 1.04 green). The registers are same as your data, but the capacitors are not same. Your 22p is 330p and 10p is 100p like the attached. I changed JRC5532 to AD4898-2 with a differential current mode to measure the performance in DSD. The board has very excellent numbers for the price. IMD is especially incredible compared to another DAC chips I have ever measured. I have no comment about SQ because I don't have an environment to listen to the board.
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File Type: jpg ESS.jpg (257.8 KB, 487 views)
File Type: jpg ESS1.jpg (347.1 KB, 481 views)
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Old 10th February 2018, 09:15 AM   #173
xx3stksm is online now xx3stksm  Japan
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Sorry I mistook the schematics. My schematics of #172 is the copy of Ver 1.04 board except for AD4898-2. I measured the board by the schematics of post #73 with AD4898-2.
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Old 10th February 2018, 10:28 AM   #174
JensH is offline JensH  Denmark
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Do you have some measurements results that you can show?
Replacing the LME49990 by ADA4898-2 probably doesn't make much difference to the results. But using current mode instead of voltage mode does.
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Old 11th February 2018, 02:09 AM   #175
madds1 is offline madds1
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Smile THS4032 ADA4898 measurements in voltage mode

Quote:
Originally Posted by JensH View Post
Do you have some measurements results that you can show?
Replacing the LME49990 by ADA4898-2 probably doesn't make much difference to the results. But using current mode instead of voltage mode does.
JensH

This indeed would be a very interesting test

I have long suspected that BW (or Slew Rate) and Settling time have more of an impact on sound quality than THD for Sigma Delta current DACs

I got this board after seeing your measurements and yes - with the standard low THD opamps (LME499990, LME49720 etc) and with 5532 - the sound was just passable and the sound seemed to correlate with your measurements

When I swapped in THS4032 - the sound improved by an order of magnitude and it was in a different league altogether. I have ordered the ADA4998 and I will report back on the sound when I get it. Tempted to try THS4012 as well

@xx3stksm

It would be very interesting to see measurements with ADA4898 or THS4032 on the board as is (not current mode)

Meanwhile - I think it behooves me to put this board in current mode and listen to it. Although last time I did these experiments with ES9018 - the sound lacked "attack" or "slam" in current mode. The sound stage and details were excellent though. The current setup with this board in voltage mode and THS4032 reminds me of ES9018 in current mode without the comprise in slam or attack

Thank you for your time and efforts gentlemen :-)
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Old 11th February 2018, 04:33 AM   #176
xx3stksm is online now xx3stksm  Japan
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The attached are my measured data about ESS9038 Ver1.04 board with AD4898-2 current mode differential output and pcm1792 for reference because a relative comparison is more understandable than absolute data.
I usually use iZptope to analyze ADC output connecting through optical SPDIF because it has many functions such as notch filter, denoise, and pitch adjustment. But next time I will use popular SW like audio Tester.

The frequency is 1.5kHz instead of 1kHz to do coherent sampling which can obtain exact bin by the rectangular window. My ADC board(AD9760), which is now under developing, can lock to the external clock which is necessary for coherent sampling. You can analyze jitter performance by 0.1Hz resolution at a 96kHz sampling with 1024K FFT.

PCM1792 has less THD than ESS9038. But the output is -0.9dBFS which means 9Vpp. I'm sure 6Vpp(2Vrms) can have better THD.
Attached Images
File Type: jpg IMG5144.jpg (910.9 KB, 408 views)
File Type: jpg ESS_D1.jpg (257.4 KB, 398 views)
File Type: jpg ess_d6.jpg (278.7 KB, 370 views)
File Type: jpg ess_p.jpg (258.0 KB, 107 views)
File Type: jpg ess_jtr.jpg (289.2 KB, 99 views)
File Type: jpg IMG_5145.jpg (990.0 KB, 148 views)
File Type: jpg pcm1.jpg (258.8 KB, 152 views)
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Old 11th February 2018, 08:38 AM   #177
JensH is offline JensH  Denmark
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It seems like your analysis SW does not show the THD. Some of the numbers are a bit confusing, e.g. the PCM1792 meaurement shows the RMS as -111.47 where the third harmonic is around -102.

What is the distortion of the ADC used for testing? At these levels of distortion a passive notch filter may be needed to see the real DAC distortion without uncertainty whether the distortion is from the DAC or from the ADC.
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Old 11th February 2018, 10:08 AM   #178
madds1 is offline madds1
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@xx3stksm

I guess you can't test the board now in its original state - I can see what you did to the DIPs

But nonetheless - interesting measurements. Surprising that THD varies as much as 10db over a period of time. The min and RMS are what I am looking at but also wonder why THD in your setup spikes (like JensH observed that the PCM1792 spiked when you took the screenshot)

@JensH - if you have a high BW opamp that runs in class A - would you be able to measure the board as is in voltage mode. :-)

Always appreciated guys.. what you do for the community
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Old 11th February 2018, 11:23 AM   #179
JensH is offline JensH  Denmark
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Quote:
Originally Posted by madds1 View Post
@JensH - if you have a high BW opamp that runs in class A - would you be able to measure the board as is in voltage mode. :-)
I don't have an op-amp that runs in class A. But I don't expect it to make any significant difference anyway.
Even with an ideal op-amp (not in stock anywhere the last time I looked), I wouldn't expect the performance to change compared to using the NJM5532.

As I see it, the distortion is created by the DAC, when operating in voltage mode, not the op-amp.
And the noise is almost entirely defined by the high resistor values in the original circuit. My measurements correlated well with simulations done in TINA TI.
Changing the op-amp from the NJM5532 to LME49720 made almost no difference. Actually I measured an increased distortion of 0.5 dB, but that could easily be measurement uncertainty, temperature differences etc.

It would probably be possible to reduce the noise of the filter/buffer by scaling the component values (lower resistor values/higher capacitor values), but I have a feeling that it might result in increased distortion due to the higher load on the DAC.

If you want low noise and low distortion,the current mode operation is the way to go.
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Old 11th February 2018, 11:28 AM   #180
cdsgames is offline cdsgames  Canada
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Quote:
Originally Posted by JensH View Post
If you want low noise and low distortion,the current mode operation is the way to go.
This is also our finding on our ess9038q2m . For best results current mode is a must.

There is a second way of increasing the SQ. Ess9038 has thd+n compensation for output stage , if you can access the registers on the dac ic , you can decrease the 2 and 3 harmonics (after you measured them). Of course you need the NDA protected datasheet.

ps. We are using discreete opamps to feed the current to..I disagree with the fact that " they don't make a difference" . Please check the whitepapers on Spakoslabs to understand the difference between monolithic and discreet opamp .

Last edited by cdsgames; 11th February 2018 at 11:31 AM.
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